Closely spaced lines or grids showing interference patterns as the scene pans across them (or even when they are static, causing a shimmering effect).

In some cases the effect is not in the video source but an artifact of playback, as in the case of analog TV sets in the United States, which are prone to creating this kind of artifact. The effect can be minimised by adding noise, at the expense of picture sharpness, when it is found to be particularly objectionable.